Noninterfering insulator



Nov. 29, 1932. K. A. HAWLEY 1,839,244

NONINTEHFERING INSULATOR Filed March 28. 9 9

grvuentof/ fl W 9" %1" I I I Patented Nov. 29, 1932 UNITED STATES PATENT OFFICE KENT A. HAWLEY, OF BALTIMORE, MARYLAND, ASSIGNOR TO LOCKE INSULATOB CORPORATION, OF BALTIMORE, MARYLAND, A CORPORATION OF IARYLAN D nonm'rnnrnmne INSULATOR Application filed larch 28, 1929. Serial No. 350,591.

The invention relates to insulators for use in connection with high tension transmission lines and has special reference to those of the pin type.

It is well known that considerable interference with radio reception is caused by the sending out of current impulses resulting from corona or current leakage across cracks, bad joints, etc. in the insulators supporting high voltage conductors. As a matter of fact, corona itself even though quite strong does not produce radio interference where one or more stages of radio fre uency amplification are involved, probably ior the reason 5 that this corona while not exactl of the character of a sixty cyclecurrent ow, is not a true high frequency phenomenon. Where there are open cracks in insulators the sparks jump through near the crest of the voltage wave. This represents a sudden vigorous current flow which sets up a local high frefluency oscillation which seriously affects raio apparatus. Unusually strong corona may act somewhat in the same manner. The

presence of cracks or fissures is generally the result of poor insulator design in the first place or ma be the result of age and the remedy is the replacement of installation. However, very strong corona is probably caused b a poor division of voltage between the insu ator parts. In the old types of insulators, the construction involved a plurality of elementary shells nested and cemented together. By way of explanation it should be mentioned that the porcelain parts with the cement between act as a group of condensers in series. Normally, the top shell carries far more than its share of the voltage through the insulator to earth and the center shell carries a little more than its share of the remainder, the reason being, probably, that the area of contact of the conductor and tie wire with the porcelain top shell is so small that the capacity of that shell as a con- 4 denser is small in proportion to the other condensers which are in the series. The rule is of course that voltage division between condensers in series is inversely proportional to their capacities. In actual practice it has 53 been found that on account of the above mentioned facts an ordinary type of insulator such as mentioned will have its top shell carrymg about forty per cent (40%) of the voltage. By experimentation it has been found that total or partial covering of the 55 top surface with a conducting material will reduce this amount by about a third or approximately twenty-eight per cent (28%). A check test recently showed the division beginning at the top of such an insulator to be twenty-eight (28) twenty-four (24) twentyone (21) and twenty-seven per cent (27%) for the respective shells or parts. This makes an insulator combination which is as near the ideal as could be expected in a commercial product.

It is known that certain manufacturers have endeavored to overcome a difliculty which exists by applying a plating of noncorrodible metal upon the top shell so as to 7 provide a conducting surface which will distribute the voltage more uniformly. However, this method is expensive and has not been in use for a sufiiciently long time to determine whether or not it will be successful. 7 5 Furthermore, this method can be employed only in new equipment as it would not be feasible to apply a coating to insulators in situ.

It is with all of the above facts in view that I have devised the present invention which has for its general object the provision of a conducting member applied to the upper shell in such manner as to be in electrical contact with the conductor.

An important object of the invention is to provide an adjunct of this character capable of being formed as a distinct entity and adapted to be applied to already existing insulators of standard pattern.

Another object of the invention is to provide a device of this type which may be applied to existing equipment by the simpleexpedient of employing a metal cap upon the top shell, the device itself being associated 5 with the cap, or to replace an existing cap with a new one with my device in association therewith.

Another important object of the invention is to provide a means of this character which will eliminate corona which tends to form at the joints between successive shells, in addition toacting as a voltage distributor.

A more specific object is to provide a device of this character which will not be subject'to deformation or destruction by freezmg.

An additional object of the invention is to provide a means of this character which will be simple and inexpensive to manufacture easy to apply, positive in action, efiicient and durable in service, and a general improvement in the art.

To the attainment of the foregoing and other objects and advantages, the invention preferably consists in the details of construction and the arrangement and combination of parts to be hereinafter more fully described and claimed, and illustrated in the accompanying drawing in which:

Figure 1 is a view partly in elevation and partly in section showing the to member of an insulator constructed to em ody the in vention, and

fFigure 2 is a fragmentary plan view there 0 Referring more particularly to the drawing it will be observed that I have shown the 7 top section of an insulator which may comrise any desired number of other sections Eelow the one shown. In this particular exemplification the insulator or section 1 has the usual outstanding skirt 2, and may be formed with any desired number of depending petticoats 3 and also a central recess 4 for the reception of a pin or post or for the accommodation of the upstanding stem portion.

of an adjacent section. This body is itself formed with an upstanding stem 5 which is generally centrally depressed at 6 and which carries a metal cap 7 having any detailed construction necessary, depending upon the character of the installation-that is to say whether the cap is to support a conductor or whether it is intended for switch and station work. In the resent instance the cap is shown as formed with a groove 8 for holding a conductor. Regardless of what the detailed formation of the cap may be, it has a depending flange 9 surrounding the stem 5 and is secured thereto by a mass of cement 10.

A conducting surface to act as a voltage distributor must extend horizontally outward from the cap and must touch the top surface of the section or shell. It is not feasible to provide an integral flange upon the cap lying upon the procelain as the abutting joint causes trouble on account of the rigidity of. the metal and the differences between the coeificients of expansion of metal and porcelain. Furthermore there is always risk of water entering and'racausing destruction when subsequent freezing occurs. With these facts in view I have desi ed alight metal member a which is indepen ent of the cap in its manumay be actuall facture but which can be readily associated therewith in operative relation thereto and to the top surface of the shell or section and which will, moreover, be free from the above enumerated disadvantages of an abutting joint between a rigid metal member and the porcelain. This member is designated in the drawing by the reference character 11 and formed as thin metal which is spun, presse or otherwise shaped to give it .the desired cross sectional curvature. Viewed in cross section, this ring member is preferably of com ound curved shape so that one edge thereo may engage upon the top surface of the body 1 with the other edge entering beneath the cap in hysical and electrical contact therewith. T e shape of this ring member 11 spaces the major ortion thereof away from t e top surface 0 the body 1 so as to define a pocket 12 within which is a mass of cement 13'which is actually a continuation of the cement 10. It is a commonpractice in insulator construction to sand or roughen the surface of the stem 5 so as to provide a grip for the cement 10 and in the present instance it is preferable that this sanded or roughened area be extended substantially to the line where the outer edge of the ring member 11 engages upon the top surface of the body 1.

In the actual assembly it is rather immaterial as to how the exact steps of connecting the parts are carried out though as a matter of fact the ring member is preferably first placed in the cap while the latter is in inverted position, subsequently to which the necessary quantit of cement is introduced within the cap, a r which the insulator section is placed, in inverted position, over the cap and moved with respect thereto to force the stem 5 into the cap. Durin the accom lishment of this the cement wil be force pocket 12, any surplus being extruded at the edge where the ring member 11 en ages a ainst the shell or section. An surp us is t en wiped off and the assemby removed from whatever holder it was supported upon and then set away for the cement to harden.

The insulator is used in exactly the same manner as any other of an equivalent type and is capable of employment for different purposes depending upon the nature of the cap used. Variations in this respect will readily suggest themselves. The metallic ring member, being in'electrical contact with the cap and consequently the conductor, will act, in accordance with well accepted theories, to distribute the voltage across whatever number'of insulator units may be provided in association with the top shell shown and described. In view of the fact that the lower outer ed e of the ring member rests upon the top sur ace of the body or section 1 corona will not form and there will be no tendency for jumping of a leakage current from the into the lit) cap to the top shell as so frequently occurs top of the body, and a continuous mass of when there is a wide cement joint. Even cement between the stem and the cap and beif by any chance moisture should be abtween the body and the rm member.

sorbed within the cement 13 beneath the rin no damage would result as the ring is of 511%- ciently light metal, as to give or yield when resultant expansion of the cement occurs. Furthermore as this ring member is flexible it would not remain distorted from such action but would return to its normal'condition or shape. The yieldability or flexibility of the ring member will prevent any undue strains coming upon the porcelain.

The above description of the mode of assembly, etc., is naturally that which would be followed in the making of new insulators. It is possible that in certain types of already existing equipment caps and metal rings might be applied. Of course, difficulties resulting from differences in styles, sizes of caps, etc., would have to be taken into consideration. From the foregoing it is believed that the construction, operation and advantages will be readily apparent to one skilled in the art without further explanation.

lVhile I have shown and described the preferred embodiment of the invention, it should be understood that the disclosure is merely an exemplification of the principles involved as the right is reserved to make all such chan es in the details of construction as will wi en the field of utility and increase the adaptability of the device provided such changes constitute no departure from the spirit of the invention or the scope of the claims hereunto appended.

Having thus described the invention, I

claim:

1. In an insulator including a dielectric body and a metal cap secured thereupon, a metallic ring member underlying the cap and overlying the body, said ring member having physical and electrical contact with the cap and having its outer edge resting directly upon the top of the body, the entire portion of the ring between its outer edge and its contact with the cap being spaced from the body.

2. In combination, an insulator comprising a body having an upstanding stem carrying a metal cap, and a metallic ring member of flexible metal secured with respect to the cap and body in underlying relation to the former and overlying relation to the latter,

said ring member having its outer portion contacting the body and its'intermediate portion spaced therefrom to define a pocket between it and the body and a mass of cement filling the pocket.

3. In an arrangement of the character described, an insulator comprising a dielectric body having an upstanding stem, a metal 'cap surrounding the stem, a flexible metal ring member of reverse curved shape in cross section having its inner edge engaged beneath the cap and its outer edge engaging up on the In testimony whereof I a KENT A. 

